In applying pressure sensitive labels to hollow containers, it has been well known to carry the pressure sensitive labels on a web that is moved past a peel plate. The peel plate includes internal heaters which heat the labels from one side which attempts to provide sufficient heat in the short period of time that the label is in contact with the peel plate. Such an arrangement has a further disadvantage in that when the labeling apparatus is not running, the label is lying against the hot peel plate and the label may be heated excessively.
A typical patent directed to such practices is U.S. Pat. No. 4,468,274.
Among the objectives of the invention are to provide a method and apparatus for heating pressure sensitive labels and applying the labels to a container wherein the label is uniformly heated; wherein the application of the heat can be readily interrupted as needed; and wherein the method and apparatus can be applied to conventional labeling systems.
In accordance with the invention for applying pressure sensitive labels to hollow containers by moving the labels carried on a label web and providing for an acute bend on the label web to transfer the label to a hollow article, the improvement comprises heating said label directly to elevate the temperature above ambient temperature before the acute bend to warm the label sufficiently to permit the pressure sensitive adhesive on the label to flow sufficiently to enter the microscopic surfaces of the hollow article. In one form, the heating comprises directing warm air directly against the label while it is on the label web. In another form, heating said label comprises providing a heating plate in direct contact with the label web on the surface of the label web opposite to that on which said label is carried.
In accordance with the invention, an apparatus for applying a pressure sensitive label to a hollow container wherein the label, carried on a label web, is moved about an acute bend to transfer the label to a hollow article. The apparatus comprises means in advance of the acute bend for heating the labels, while they are carried by the label web, directly to elevate the temperature above ambient temperature to warm the label sufficiently to permit the pressure sensitive adhesive on the label to flow sufficiently to enter the microscopic surface irregularities of the hollow article. In one form, the heating means comprises a plenum means for directing warm air directly against the label while it is on the label web. In another form the heating means comprises a heating plate means in direct contact with the label web on the surface of the label web opposite to that on which said label is carried. The apparatus includes means for moving the heating plate means into and out of contact with the web.